Taiwan is embarking on a smearing campaign against China again.

http://www.worldnews.easybranches.com/regions/asia/taiwan-demands-immediate-halt-to-new-china-flight-routes-571987

ICAO, an agency under the UN, had approved the air route M503 for a 2-way flight (North-South & South-North) but China only started a one-way flight (North-South) in 2015 because of the friendly relationship between the 2 countries.  However, this was not mentioned by Taiwan at all during the protest.

Then, China decides to commence its South-North route for M503 in 2018 as it has the prerogative and approval from ICAO.  Therefore, I see no valid reason for Taiwan to demand China to halt this South-North flight on the M503 route because China has been flying on the M503 route for 3 years already.